If you have upgraded your Macintosh computer to High Sierra (10.3), please update your Macintosh with the latest security patch released this morning, 12/29.
Yesterday, 12/28, a major security flaw was discovered in High Sierra Apple’s latest Macintosh operating system released on September 5th. Earlier versions are not affected.
The flaw allows anyone with access to the computer, even if the computer is locked, to gain administrator access to the computer.
Apple has released an update via the App Store application which fixes the flaw. This update should be applied as soon as possible on all Macintosh computers running High Sierra.